CEREBRAL OXYGENATION DURING WARMING AFTER CARDIOPULMONARY BYPASS

Objectives: To evaluate jugular venous oxygen saturation (Sj(v) over b ar o(2)), measured with a fiberoptic oximetry catheter, and brain tiss ue oxygen saturation, measured by near-infrared spectroscopy (NIRSO2), as monitors of cerebral oxygenation during cardiopulmonary bypass sur gery. Design: Prospective, clinical study. Setting: Operating room of a Veterans Administration Hospital. Patients: Nineteen patients underg oing moderate hypothermic cardiopulmonary bypass surgery. Intervention s: Sj(v) over bar o(2) and NIRSO2 were monitored in the patients durin g the surgical procedure. Measurements and Main Results: Moderate hypo thermic cardiopulmonary bypass surgery had two distinct cerebral hemod ynamic phases. While the patients were hypothermic, Sj(v) over bar o(2 ) averaged 80 +/- 7% and none of the patients had an increase in cereb ral lactate production. During the rewarming period, however, reductio ns in Sj(v) over bar o(2) to <50% occurred in 16 (84%) patients and in creased cerebral anaerobic metabolism developed in 11 (58%) patients. Sj(v) over bar o(2) during rewarming was dependent on mean arterial pr essure, with 60 mm Hg appearing to be a critical value. Two other fact ors appeared to also contribute to the jugular desaturation, a low hem atocrit and a rapid warming time. The Sj(v) over bar o(2) catheter had excellent performance during the surgery. The average difference betw een paired measurements of Sj(v) over bar o(2) by the catheter and in blood samples was -0.4 +/- 4.25%, and the correlation between the two measurements was highly significant (r(2)=.93; P<.001). The NIRSO2 tre nded with the Sjvo(2) in most patients (r(2)=.63; P<.001), Conclusions : The study confirms other studies showing that jugular venous desatur ation can occur during rewarming after cardiopulmonary bypass surgery. Presently, Sj(v) over bar o(2) appears to be a better monitor of cere bral oxygenation than NIRSO2. However, NIRSO, has promise as a noninva sive monitor of cerebral oxygenation if future developments allow more quantitative measurements of oxygen saturation.